Methods of protection from toxicity of alpha emitting elements during radioimmunotherapy

ABSTRACT

Provided herein are methods of reducing nephrotoxicityfrom at least one alpha particle-emitting daughter of actinium-225 during radioimmunotherapeutic treatment for a pathophysiological condition, methods of improving radioimmunotherapeutic treatment of cancer and methods of increasing the therapeuticindex of an actinium-225 radioimmunoconjugate during treatment of a pathophysiological condition. Adjuvants effective for preventing accumulation of  225 Ac daughters within the kidneys are administered during treatment with an actinium-225 radioimmunoconjugate to reduce nephrotoxicity. Examples of adjuvants are chelators, diuretics and/or competitive metal blockers.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This nonprovisional application claims benefit of priority ofprovisional application U.S. Serial No. 60/457,503, filed Mar. 25, 2003,now abandoned.

FEDERAL FUNDING LEGEND

[0002] This invention was produced in part using funds obtained throughgrant R01-CA 55349 from the National Institutes of Health. Consequently,the federal government has certain rights in this invention.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates generally to the fields ofradioimmunotherapy and cancer treatment. Specifically, the presentinvention provides methods of protecting an individual from toxicity ofalpha particle-emitting elements during radioimmunotherapy.

[0005] 2. Description of the Related Art

[0006] Monoclonal antibody (mAb) based therapies are ideally applicableto the hematopoietic neoplasms (1) because of readily accessibleneoplastic cells in the blood, marrow, spleen and lymph nodes whichallow rapid and efficient targeting of specific mAb's. The wellcharacterized immunophenotypes of the various lineages and stages ofhematopoietic differentiation has enabled identification of antigentargets for selective binding of mAb to neoplastic cells whilerelatively sparing other necessary hematopoietic lineages and progenitorcells. Similar work is now being carried out for a variety of solidcancers as well.

[0007] In some models of leukemia, specific uptake of antibodies ontotarget cells can be demonstrated within minutes, followed by losses ofmAb from the cells by modulation (2,3). Similar modulation has been seenin pilot studies in acute leukemia in humans (4-7). Based on thisbiology and pharmacokinetics, it has been proposed that mAb tagged withshort-lived nuclides emitting short-ranged, high linear energy transfer(LET) alpha particles (8-9) or short-ranged auger electrons (10-11), maybe effective in therapy. These short-ranged particles may be capable ofsingle cell kill while sparing bystanders.

[0008] Pilot trials conducted in patients with hematopoieticcancers(4-7,12) have demonstrated the ability of mAb to bind to target cellsand have also highlighted the problems of antigen modulation, antigenheterogeneity, tumor burden and human anti-mouse antibody (HAMA)response (4-7,12-16). Some short-lived major tumor responses were seenin these early trials with non-cytotoxic antibodies. More consistentresponses were next achieved in recent trials using cytotoxic mAb andisotope tagged mAb (17-24). Two antibodies to CD20 are now approved forthe treatment of non-Hodgkin's lymphoma (24-26). Recently, one antibodyfor treating AML and one for CLL were also approved. (26-28). A largesystematic in vivo study of various antibody-based immuno-therapies inacute myelogenous leukemia with more than 300 treated patients has beenconducted (4,19,21,29-31).

[0009] The expression of the CD33 antigen is restricted to myelogenousleukemias and myeloid progenitor cells, but not to other normal tissuesor ultimate bone marrow stem cells (32-35). In summary it has beendemonstrated that HuM195 is highly specific for myeloid leukemia cellsboth in vitro and in vivo; HuM195 does not react with tissue or cells ofother types or neoplastic cells not of myeloid origin. HuM195 reactswith early myeloid progenitors, but not stem cells, and reacts withmonocytes and dendritic cells, but no other mature hematopoieticelements. HuM195 mAbs have high affinities, i.e., on the order of 10⁻⁹to 10⁻¹⁰ M. M195 mAbs are internalized into target cells after binding.

[0010] A series of early studies defined the pharmacology, safetyprofile, biodistribution, immunobiology, and activity of various M195agents. M195 showed targeting to leukemia cells in humans (4).Adsorption of M195 onto leukemic target cells in vivo was demonstratedby biopsy, pharmacology, flow cytometry, and imaging; saturation ofavailable sites occurred at doses 5 mg/m². The entire bone marrow wasspecifically and clearly imaged beginning within minutes afterinjection; optimal imaging occurred at 5-10 mg dose levels. Bone marrowbiopsies demonstrated significant dose-related uptake of M195 as earlyas 1 hour after infusion in all patients with the majority of the dosefound in the marrow. M195 was rapidly modulated with a majority of thebound IgG being internalized into target cells in vivo.

[0011] Other trials showed that radiolabeled beta emitting M195, witheither I-131 or Y-90, can effect up to 100% cytoreduction of leukemiccells (19). Most patients had reduction in their leukemia burden withprolonged marrow hypoplasia achieved at higher dose levels. Thesepatients were taken to BMT and nearly all achieved CR with severalultimately cured.

[0012] A wide variety of nuclides suitable for mAb-guided radiotherapyhave been proposed (12). Depending on the particular application, threeclasses of radionuclides may prove therapeutically useful in leukemia(9-11, 17, 19-23,36-44): β-emitters (¹³¹I, ⁹⁰Y) with long range (1-10mm) emissions are probably limited to settings of larger tumor burdenwhere BMT rescue is feasible. Alpha-emitters (²¹³Bi, ²¹¹At) with veryhigh energy but short ranges (0.05 mm) may allow more selective ablation(37-51). Auger emitters (¹²³I, ¹²⁵I) which act only at subcellularranges (<1 micron) will yield single cell killing but only ifinternalized.

[0013] Radioimmunotherapy has advanced tremendously in the last 20 yearswith the development of more sophisticated carriers, as well as ofradionuclides optimized for a particular cancer and therapeuticapplication (52). Radioimmunotherapy (RIT) with alpha particle emittingradionuclides is advantageous because alpha particles have high LET andshort path lengths (50-80 μm) (53-57). Therefore, a large amount ofenergy is deposited over a short distance, which renders alpha particlesextremely cytotoxic with a high relative biological effectiveness(55-56). Little collateral damage to surrounding normal,antigen-negative cells occurs (57-59). A single traversal of denselyionizing, high energy alpha particle radiation through the nucleus, maybe sufficient to kill a target cell (60). In addition, the doublestranded DNA damage caused by alpha particles is not easily repaired bythe cells, and this cytotoxicity is largely unaffected by the oxygenstatus and cell-cycle position of the cell (53).

[0014] The results of pre-clinical studies with alpha particle emitting²²⁵Ac atomic nanogenerators have generated optimism for their humanclinical use (61-62). ²²⁵Ac has a sufficiently long half-life (10 days)for feasible use and it decays to stable Bismuth-209 via six atoms,yielding a net of four alpha particles (FIG. 1). This permits deliveryof radiation even to the less readily accessible cells and also for theradiopharmaceutical to be shipped world-wide (61).

[0015]²²⁵Ac is successfully coupled to internalizing monoclonalantibodies using DOTA(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) as thechelating moiety. The ²²⁵Ac-DOTA-antibody construct acts as atumor-selective, molecular-sized, in-vivo atomic generator, i.e., atargetable nanogenerator, of alpha particle emitting elements (61). The²²⁵Ac-DOTA-antibody constructs are stable in-vivo and have been shown tobe safe and potent anti-tumor agents in mouse models of solidprostatatic carcinoma, disseminated lymphoma and intraperitoneal ovariancancer (61-62). The safety of ²²⁵Ac-HuM195 and ²²⁵Ac-3F8 at low doses,has been demonstrated in primates (63).

[0016]²²⁵Ac decays via its alpha-emitting daughters, Francium-221(²²¹Fr), Astatine-217 (217 At) and Bismuth-213 (²²¹Bi) to stable,non-radioactive ²⁰⁹Bi (58,60,63). These daughters, once formed, areunlikely to associate with the antibody-DOTA construct due to highatomic recoil-energy as a result of alpha decay (65), possible ruptureof the chelate and different chemical properties of the daughters. Thedaughters generated and retained inside the cancer cell afterinternalization of the ²²⁵Ac labeled antibody, add to itscytotoxiceffect (61). Although this property greatly enhances thepotency of the ²²⁵Ac nanogenerators, it could also result in toxicity asthe systemically released radioactive daughters may get transported toand irradiate the normal tissues. The ²²⁵Ac-immunoconjugate is stable invivo and the daughters released inside the target cell remaininternalized (61). However, the daughters released from the circulating²²⁵Ac nanogenerator, tend to distribute independently of the parentconstruct (63).

[0017] Tumor burden is an important determinant in the biodistributionof the antibody (16, 65). However, the free daughters produced in thevasculature from the circulating unbound antibody or the antibody boundto the surface of a target cell, could diffuse or be transported tovarious target organs where they can accumulate and cause radiotoxicity.Bismuth is known to accumulate in the renal cortex (66-69). It has beenobserved that after injection in mice, francium rapidly accumulates inthe kidneys (unpublished result). Francium distribution in the body hasnot been described due to its short half-life that makes experimentalstudy difficult (69).

[0018] Monkeys injected with escalating doses of the untargeted ²²⁵Acnanogenerator developed a delayed radiation nephropathy manifesting asanemia and renal failure (63). Therefore, a possible hindrance to thedevelopment of these agents as safe and effective cancer therapeutics islikely to be their nephrotoxicity. By preventing the renal accumulationof the radioactive daughters or by accelerating their clearance from thebody, the therapeutic-index of the ²²⁵Ac nanogenerator could beenhanced.

[0019] Astatine-217 has the shortest half-life of 32 ms of thealpha-emitting daughters of ²²⁵Ac. It decays almost instantaneously to²¹³Bi. ²¹³Bi and ²²¹Fr have relatively longer half-lives of 45.6 min.and 4.9 min., respectively, and therefore, have the potential to causeradiation damage (61,59). The presence of bismuth-binding,metallothionein-like proteins in the cytoplasm of renal proximal tubularcells, makes the kidney a prime target for the accumulation of free,radioactive bismuth (66-68). Dithiol chelators have been shown tochelate bismuth and enhance its excretion in various animal as well ashuman studies (64,69,71-72). Dithiol chelators also enhanced the totalbody clearance of the gamma emitting tracer, ²⁰⁶Bi acetate (12).Chelators such as ethylenediamine tetraacetic acid (EDTA) ordiethylenetriamine pentaacetic acid (DTPA) also may chelate such metals.Ca-DTPA has been used in the U.S. as a chelating agent for plutonium andother transuranic elements (73-74).

[0020]²²¹Fr is another potentially toxic daughter of ²²⁵Ac. Francium,like sodium and potassium, is an alkali metal. Furosemide and thiazidediuretics are known to increase urine output and accelerate theelimination of sodium and potassium in urine, by inhibiting theirreabsorption in different segments of the nephron (75).

[0021] The inventors have recognized a need in the art to improve thesafe and efficacious use of ²²⁵Ac as a stable and extraordinarily potenttumor-selective molecular sized generator in both established solidcarcinomas or in disseminated cancers. Specifically, the prior art islacking in methods of using, individually or in combination, adjuvantchelation, diuresis or competitive metal blockade to reducenephrotoxicity from ²²⁵Ac daughters generated during radioimmunotherapy.The present invention fulfills this long-standing need and desire in theart.

SUMMARY OF THE INVENTION

[0022] The present invention is directed to a method of reducingnephrotoxicity in an individual during radioimmunotherapeutic treatmentof a pathophysiological condition. A pharmacologically effective dose ofat least one adjuvant effective for preventing accumulation of a metalin kidneys and an actinium-225 radioimmunoconjugate to treat thepathophysiological condition are administered to the individual.Accumulation of an alpha particle-emitting daughter of the actinium-225within the kidneys of the individual is prevented via interactionbetween the adjuvant and the ²²⁵Ac daughter or the kidney tissue or acombination thereof thereby reducing nephrotoxicity during theradioimmunotherapeutic treatment.

[0023] The present invention is directed to related methods of reducingnephrotoxicity in an individual by administering a diuretic alone or incombination with the chelator and administering an actinium-225radioimmunoconjugate to treat the pathophysiological condition. Thechelator scavenges bismuth-213 daughters of actinium-225. The diureticinhibits reabsorption of francium-211 daughters of actinium-225 withinthe kidneys to prevent accumulation thereof to reduce nephrotoxicity.

[0024] The present invention also is directed to a method of improvingradioimmunotherapeutic treatment of cancer in an individual. Asdescribed above a pharmacologically effective dose of a chelator and anactinium-225 radioimmunoconjugate are administered individually. Thechelator scavenges bismuth-213 daughters of the actinium-225 to reducenephrotoxicity in the individual during treatment thereby increasing thetherapeutic index of the actinium-225 to improve the treatment forcancer.

[0025] The present invention also is directed to related methods ofimproving radioimmunotherapeutic treatment of cancer by reducingnephrotoxicity in the individual during treatment thereby increasing thetherapeutic index of the actinium-225 to improve the treatment for thecancer. A diuretic alone or in combination with the chelator and anactinium-225 radioimmunoconjugate are administered individually to theindividual. The chelator functions as described above. The diureticinhibits renal uptake of francium-211 daughters within the kidneys toreduce nephrotoxicity.

[0026] The present invention is directed further to a method ofincreasing the therapeutic index of an actinium-225 radioimmunoconjugateduring treatment of a pathophysiological condition in an individual.Renal uptake of at least one alpha particle-emitting daughter ofactinium-225 is inhibited whereby nephrotoxicity is reduced during thetreatment thereby increasing the therapeutic index of said actinium-225radioimmunoconjugate. In related methods inhibition of renal uptake of²²⁵Ac daughters is accomplished by administering a pharmacologicallyeffective amount of an adjuvant comprising a chelator to scavenge the²²⁵Ac daughters therewith or of a diuretic to inhibit reabsorption ofthe ²²⁵Ac daughters within a kidney or of a competitive metal blocker toprevent binding of ²¹³Bi within a kidney or a combination of a chelator,a diuretic and the competitive metal blocker.

[0027] Other and further aspects, features, and advantages of thepresent invention will be apparent from the following description of thepresently preferred embodiments of the invention. These embodiments aregiven for the purpose of disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The appended drawings have been included herein so that theabove-recited features, advantages and objects of the invention willbecome clear and can be understood in detail. These drawings form a partof the specification. It is to be noted, however, that the appendeddrawings illustrate preferred embodiments of the invention and shouldnot be considered to limit the scope of the invention.

[0029]FIG. 1 depicts a simplified Ac-225 generator to Bi-213 decayscheme, yielding 4 net alphas. The half-lives are shown in italics.

[0030]FIG. 2 depicts the structures of 2,3 dimercapto-1-propanesulfonicacid (DMPS) and meso 2,3 dimercaptosuccinic acid (DMSA)

[0031]FIGS. 3A-3B compare the effect of dithiol chelators on ²¹³Bidistribution in kidneys and blood. FIG. 3A compares reduction in therenal ²¹³Bi activity by DMPS or DMSA treatment at 6 hours and 72 hourspost-injection. The renal ²²¹Fr activity is unchanged at bothtime-points. FIG. 3B compares the increase in the ²¹³Bi activity inblood by chelation therapy with DMPS or DMSA at 6 hours and 72 hourspost injection. Data are mean (SE). % ID/g=percentage of injected doseper gram of tissue.

[0032]FIGS. 4A-4B depict the effect of diuresis or a combination ofmetal chelation and diuresis on renal ²²¹Fr and ²¹³Bi activity. FIG. 4Ashows the reduction in the 24 hour renal ²²¹Fr and ²¹³Bi activities byfurosemide and chlorothiazide (CTZ) treatment. FIG. 4B shows the reducedrenal accumulation of ²²¹Frand ²¹³Bi at 24 hours post-injection bycombination therapy with DMPS and furosemide or CTZ. Data are mean (SE).% ID/g=percentage of injected dose per gram of tissue.

[0033]FIG. 5 depicts the effect of competitive metal blockade on ²²⁵Acdaughter distribution and shows the reduction in the renal ²¹³Biactivity by bismuth subnitrate (BSN) at 6 hours and 24 hourspost-injection.

[0034]FIGS. 6A-6C depict the effect of tumor burden on ²²⁵Ac daughterdistribution. FIG. 6A compares the percentage of human-CD20 cells in thebone marrow of a “high burden” and a “low burden” animal to that of anon tumor-bearing mouse of the same strain. FIG. 6B shows the reductionin the ratio of kidney to femur activity for ²²⁵Ac and ²¹³Bi in animalswith higher tumor burden. DMPS treatment further reduced the kidney tofemur activity ratio for ²¹³Bi. FIG. 6C shows the reduction in the renal²¹³Bi activity by the presence of higher tumor burden, and furtherenhancement of the effect by concomitant DMPS treatment. Error barsdenote SE. % ID/g=percentage of injected dose per gram of tissue.

[0035]FIG. 7 depicts the biodistribution of [Ac]Hum195 at 24 hours inDMPS-treated and untreated monkeys.

DETAILED DESCRIPTION OF THE INVENTION

[0036] In one embodiment of the present invention there is provided amethod of reducing nephrotoxicity in an individual duringradioimmunotherapeutic treatment of a pathophysiological conditioncomprising administering a pharmacologically effective dose of at leastone adjuvant effective for preventing accumulation of a metal inkidneys; administering an actinium-225 radioimmunoconjugate to treat thepathophysiological condition; and preventing accumulation of alphaparticle-emitting daughters of the actinium-225 within the kidneys ofthe individual via interaction between the adjuvant and the ²²⁵Acdaughters or the kidney tissue or a combination thereof thereby reducingnephrotoxicity during the radioimmunotherapeutic treatment. In an aspectof this embodiment the adjuvant(s) may be administered prior toadministering the actinium-225 radioimmunoconjugate with the adjuvant(s)continuing to be administered after the actinium-225radioimmunoconjugate.

[0037] In other aspects of this embodiment the adjuvant maybe achelator, a diuretic, a competitive metal blocker or a combination ofthese. Representative examples of a chelator are 2,3dimercapto-1-propane sulfonic acid, meso 2,3-dimercapto succinic acid,diethylenetriamine pentaacetic acid, calcium diethylenetriaminepentaacetic acid, or zinc diethylenetriamine pentaacetic acid. Examplesof a diuretic are furosemide, chlorthiazide, hydrochlorothiazide, bumexor other loop diuretic. The competitive metal blocker may be bismuthsubnitrate or bismuth subcitrate. In these aspects the ²²⁵Ac daughtermay be bismuth-213, francium-221 or a combination thereof.

[0038] In all aspects the actinium-225 radioimmunoconjugate may comprisean actinium-225 bifunctional chelant and a monoclonal antibody. Anexample of such a radioimmunoconjugate is [²²⁵Ac] DOTA-HuM195. Furtherto all aspects the pathophysiological condition may be a cancer or anautoimmune disorder. The cancer may be a solid cancer, a disseminatedcancer or a metastatic cancer. A representative cancer is myeloidleukemia.

[0039] In a related embodiment there is provided a method of reducingnephrotoxicity in an individual during radioimmunotherapeutic treatmentof a pathophysiological condition comprising administering apharmacologically effective dose of a chelator; administering anactinium-225 radioimmunoconjugate to treat the cancer; and preventingaccumulation of bismuth-213 daughters of the actinium-225 within thekidneys of the individual by scavenging thereof with the chelatorthereby reducing nephrotoxicity during the radioimmunotherapeutictreatment.

[0040] Further to this embodiment the method comprises administering apharmacologically effective dose of a diuretic and preventingaccumulation of francium-211 daughters of the actinium-225 within thekidneys of the individual by inhibiting reabsorption of francium-211therein with the diuretic thereby reducing nephrotoxicity during theradioimmunotherapeutic treatment.

[0041] In another related embodiment there is provided a method ofreducing nephrotoxicity in an individual during radioimmunotherapeutictreatment of a pathophysiological condition comprising administering apharmacologically effective dose of a diuretic; administering anactinium-225 radioimmunoconjugate to treat the cancer; and preventingaccumulation of francium-211 daughters of the actinium-225 within thekidneys of the individual by inhibiting reabsorption of francium-211therein with the diuretic thereby reducing nephrotoxicity during theradioimmunotherapeutic treatment.

[0042] In all of these related embodiments the chelators and thediuretics are as described supra. Additionally, the points ofadministration of the chelator and/or the diuretic during treatment areas described supra. Furthermore, in these related embodiments the ²²⁵Acradioimmunoconjugate and the cancers treated are as described supra.

[0043] In another embodiment of the present invention there is provideda method of improving radioimmunotherapeutic treatment of a cancer in anindividual, comprising administering a pharmacologically effective doseof a chelator; administering an actinium-225 radioimmunoconjugate; andscavenging bismuth-213 daughters of the actinium-225 with the chelatorto reduce nephrotoxicity in the individual during the treatment therebyincreasing the therapeutic index of the actinium-225 to improve thetreatment for cancer. Further to this embodiment there is provided amethod of administering a pharmacologically effective dose of adiuretic; and inhibiting renal uptake of francium-211 daughters of theactinium-225 with the diuretic to reduce nephrotoxicity in theindividual during the treatment thereby increasing the therapeutic indexof the actinium-225 to improve the treatment for the cancer.

[0044] In a related embodiment there is provided a method of improvingradioimmunotherapeutic treatment of cancer in an individual, comprisingadministering a pharmacologically effective dose of a diuretic;administering an actinium-225 radioimmunoconjugate; and inhibiting renaluptake of francium-211 daughters of the actinium-225 with the diureticto reduce nephrotoxicity in the individual during the treatment therebyincreasing the therapeutic index of the actinium-225 to improve thetreatment for the cancer.

[0045] For all these embodiments the chelators and the diuretics aredescribed supra, as are the points of administration of the chelatorand/or the diuretic during treatment. Again in these embodiments the²²⁵Ac radioimmunoconjugate and the cancers treated are as describedsupra.

[0046] In yet another embodiment there is provided a method ofincreasing the therapeutic index of an actinium-225 radioimmunoconjugateduring treatment of a pathophysiological condition in an individualcomprising inhibiting renal uptake of at least one alphaparticle-emitting daughter of actinium-225 whereby nephrotoxicity isreduced during the treatment thereby increasing the therapeutic index ofthe actinium-225 radioimmunoconjugate.

[0047] In an aspect of this embodiment the step of inhibiting renaluptake comprises administering a pharmacologically effective amount ofan adjuvant comprising a chelator to scavenge the ²²⁵Ac daughterstherewith or of a diuretic to inhibit reabsorption of the ²²⁵Acdaughters within a kidney, or a competitive metal blocker to preventbinding of said ²²⁵Ac daughters within a kidney or a combinationthereof. An example of an ²²⁵Ac daughter scavenged by a chelator isbismuth-213. An example of an ²²⁵Ac daughter that is inhibited fromreabsorbing into the kidneys is francium-211. An example of an ²²⁵Acdaughter that is prevented from binding within a kidney is ²¹³Bi.

[0048] In all embodiments and aspects thereof, the pathophysiologicalcondition may be a cancer or an autoimmune disorder. The cancer may be asolid cancer, a disseminated cancer or a micrometastatic cancer. Anexample of a cancer is myeloid leukemia. Furthermore, the chelators, thediuretics, the competitive metal binders, the points of administrationthereof during treatment, the ²²⁵Ac radioimmunoconjugate and the cancerstreated are as described supra.

[0049] As used herein “radioimmunotherapy” shall refer to targetedcancer therapy in which a radionuclide is directed to cancer cells byuse of a specific antibody carrier.

[0050] As used herein, “alpha particle” shall refer to a type ofhigh-energy, ionizing particle ejected by the nuclei of some unstableatoms that are relatively heavy particles, but have low penetration.

[0051] As used herein, “radionuclide” shall refer to any element thatemits radiation from its nucleus.

[0052] As used herein, “²²⁵Ac nanogenerator”shall refer to a nano-scale,in-vivo generator of alpha particle emitting radionuclide daughters,produced by the attachment of a chelated Actinium-225 atom to amonoclonal antibody.

[0053] Provided herein are methods of controlling renal uptake ofactinium-225 daughters generated by an ²²⁵Ac nanogenerator duringtargeted radioimmunotherapy which accelerate the clearance of the alphaparticle-emitting daughters from the body. Methods utilizing metalchelation, diuresis, or competitive metal blockade may be used asadjunct therapies to modify the potential nephrotoxicity of ²²⁵Acdaughters. Generally, a radioimmunoconjugate comprising an ²²⁵Acnanogenerator will bind a targeted tumor cell. Upon binding theactinium-255 decays and delivers the alpha particle-emitting daughtersto the cell to effect treatment. Once the decay cascade sequence begins,however, the daughter radiometals are no longer bound to the antibodyand all daughters are not delivered to the targeted tumor cell. Thus,the daughters are free to accumulate in healthy tissues such as thekidneys causing toxicity.

[0054] Chelated metals are protected and are, therefore, safe ifdetached from the antibody due to their rapid renal clearance. Chelatorssuch as, but not limited to, the dithiol chelators 2,3dimercapto-1-propane sulfonic acid (DMPS) and meso 2,3-dimercaptosuccinic acid (DMSA) shown in FIG. 2 or other chelators, e.g.,ethylenediamine tetra-acetic acid (EDTA), diethylenetriamine pentaaceticacid (DTPA), calcium diethylenetriamine pentaacetic acid (Ca-DTPA), orzinc diethylenetriamine pentaacetic acid (Zn-DTPA),may be used toprevent the accumulation of free bismuth-213 daughters in the patient.Preferably, DMPS is used to chelate bismuth-213 daughters.

[0055] The present invention also provides methods of using diuretics toreduce renal uptake of francium-211 daughters and, by extension as adecay product thereof, bismuth-213 daughters into the nephron viainhibition of reabsorption of francium-211 through diuresis. Examples ofsuch diuretics are furosemide, chlorthiazide, hydrochlorothiazide,bumex, or other loop diuretic. Additionally, competitive metal blockersmay be used to compete with bismuth-213 for binding sites in the renaltubular cells of the kidney. Examples of a nonradioactive bismuthcompetitor are bismuth subnitrate or bismuth subcitrate.

[0056] Thus, as described herein, adjuvants, e.g., chelators, diureticsor competitive metal blockers, either individually or in combination,may be used as an adjunct chelating therapy to modify the nephrotoxicityof bismuth-213 and/or francium-211. Combination of adjuvant therapiesresults in cumulative effects over individual therapies. Therefore,nephrotoxicity is reduced during treatment and larger and more effectivedoses of the ²²⁵Ac nanogenerator may be administered. This may allow upto a doubling or more of the therapeutic index of suchradiochemotherapeutics. As such, radioimmunotherapeutic treatment ofpathophysiological conditions, such as but not limited to, cancers,e.g., leukemias, and autoimmune disorders are improved.

[0057] In the ²²⁵Ac nanogenerator the actinium-225 may be stably boundto a monoclonal antibody via a bifunctional chelant, such as a modified1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) whichchelates the actinium-225 while binding it to the monoclonal antibody.Although not limited to such, an example of a radioimmunoconjugate (RIC)suitable for targeted therapy of myeloid leukemia cells is the ²²⁵Acnanogenerator [²²⁵Ac] DOTA-HuM195.

[0058] Additionally, the methods provided herein are more efficacious inreducing nephrotoxicity in patients with a higher tumor burden. Thepresence of high levels of a specific target tumor burden caused adecrease in the amount of circulating, untargeted antibody and,therefore, the systemically released daughters. Furthermore, the ²²⁵Acnanogenerator comprises a monoclonal antibody that is internalizedwithin the target tumor cells. Therefore, a sub-saturating amount ofantibody, e.g., about 2-3 mg of HuM195, administered to a patientresults in more of the generated daughters being retained inside thecancer cell because, theoretically,almost all of the antibody should beable to bind to the target cells and be internalized.

[0059] It is contemplated that the adjunct methods described herein maybe used with targeted ²²⁵Ac nanogenerator radioimmunotherapy ofpathophysiological conditions benefiting from ²²⁵Ac radioimmunotherapy.For example, the methods presented herein may be used in conjunctionwith radioimmunotherapeutic methods for treatment of solid cancers,disseminated cancers and micrometastatic cancers. Thus, leukemias, suchas myeloid leukemia, may benefit from this adjunct therapy. It isfurther contemplated that other diseases or disorders for which ²²⁵Acnanogenerator would be administered may benefit from these adjuvants. Anexample of such a disorder is an autoimmune disorder.

[0060] The adjuvants of the present invention may be administered priorto the ²²⁵Ac nanogenerator with continued administration after theradioimmunotherapeutic treatment. Routes of administration may be eitheroral or via injection, such as intravenous injection, and are well knownto those of ordinary skill in the art.

[0061] It is also contemplated that administration of the adjuvantchelators, diuretics and competitive metal blockers is via anappropriate pharmaceutical composition. In such case, the pharmaceuticalcomposition comprises the adjuvant and a pharmaceutically acceptablecarrier. Such carriers are preferably non-toxic and non-therapeuticPreparation of such pharmaceutical compositions suitable for the mode ofadministration is well known in the art.

[0062] The adjuvants are administered in an amount to demonstrate apharmacological effect, e.g., an amount to reduce nephrotoxicity due tobismuth-213 or francium-211 accumulation within the kidneys. Anappropriate dosage may be a single administered dose or multipleadministered doses. The doses administered optimize effectivenessagainst negative effects of radioimmunotherapeutic treatment. As withall pharmaceuticals, including the ²²⁵Ac nanogenerator described herein,the amount of the adjuvant administered is dependent on factors such asthe patient, the patient's history, the nature of the cancer treated,i.e., solid or disseminated, the amount and specific activity of theactinium generator construct administered and the duration of theradioimmunotherapeutic treatment.

[0063] As the adjuvants of the present invention are approved andavailable for human use, the amounts administered would typically fallwithin recommended usage guidelines designated by the package inserts orby the general practice of medicine. For example, doses of DMPS may bein the recommended range of 0.1-1 mmol/kg/d for the treatment of heavymetal poisoning (64). An example of a dosing regimen for DMSA may beabout 10 mg/kg every 8 hours and for DMPS may be 200-1500 mg/day individed doses.

[0064] It is contemplated that use of the adjuvant therapies describedherein would allow significant escalation of patient doses ofactinium-225. A therapeutic dose of an adjuvant where the ratio ofavailable adjuvant molecules to ²¹³Bi atoms or ²¹¹Fr atoms issubstantially high provides for a significant reduction innephrotoxicity. Therefore, with a capability to clear free actinium-225daughters greater than the daughters generated for a given dose, higherdoses of the ²²⁵Ac nanogenerator may be administered with a reduced riskof subsequent nephrotoxicity during treatment. A dose of about 0.5μCi/kg to about 5.0 μCi/kg of actinium-225 may be used to treat thepatient. A representative example is about 1 μCi/kg of actinium-225.However, determination of dosage of the adjuvants described herein andof the ²²⁵Ac nanogenerator is well within the skill of an artisan in thefield and may be determined to be any therapeutically effective amountusing at least the criteria discussed supra.

[0065] As described herein, the invention provides a number oftherapeutic advantages and uses. The embodiments and variationsdescribed in detail herein are to be interpreted by the appended claimsand equivalents thereof. The following examples are given for thepurpose of illustrating various embodiments of the invention and are notmeant to limit the present invention in any fashion.

EXAMPLE 1

[0066] Animals

[0067] Female BALB/cand severe combined immunodeficient (SCID) mice,4-12 weeks of age, were obtained from Taconic, Germantown, N.Y.Cynomologus monkeys were obtained. All animal studies were conductedaccording to the NIH Guide for the care and use of laboratory animalsand were approved by the Institutional Animal Care and Use committee atMemorial Sloan Kettering Cancer Center.

EXAMPLE 2

[0068] Preparation and Quality Control of Actinium-225 LabeledAntibodies

[0069]²²⁵Ac was conjugated to SJ25C1, a mouse anti-human CD19 IgG1monoclonal antibody (Monoclonal Antibody Core Facility, Memorial SloanKettering Cancer Center) or HuM195, a humanized anti-CD33 IgG1monoclonal antibody; (Protein Design Labs, Fremont, Calif.) using atwo-step labelling method, as described previously (76). Routine qualitycontrol of the labeled antibody was performed using instant thin layerchromatography (ITLC) to estimate the radio-purity (62,77).

EXAMPLE 3

[0070] Administration of Actinium-225 Nanogenerator to Mice

[0071] The mice were anesthetized and then injected intravenously in theretro-orbital venous plexus with 0.5 μCi of either ²²⁵Ac labeled HuM195for chelation, diuresis and competitive metal blockade experiments or of²²⁵Ac labeled SJ25C1 for tumor burden experiments. The injected volumewas 100 μl. In order to detect adequate numbers of disintegrations intissues by use of the gamma-counter, the injected doses of ²²⁵Acnanogenerator, i.e., ˜30 μCi/kg, are much higher than the doses forhuman clinical trials with these adjuvants.

EXAMPLE 4

[0072] Statistical Analysis

[0073] Graphs were constructed using Prism (Graphpad Software Inc.,SanDiego, Calif.). Statistical comparisons between experimental groupswere performed by either the Student's t-test (two-group comparison) orone-way ANOVA with Bonferroni's multiple comparison post-hoc test(three-group comparison). The level of statistical significance was setat p<0.05.

[0074] The inter-experiment variance in the tissue daughter activitiesat a given time-point was expected due to possible age-relatedvariability in the capacity of the reticuloendothelial system tometabolize the labeled antibody. However, the intra-experimentvariability within an experimental group was very small.

EXAMPLE 5

[0075] Free Metal Scavenging with DMPS or DMSA

[0076] Animals received either 2,3-dimercapto-1-propanesulfonic acid(DMPS; Sigma, St. Louis, Mo.) or meso-2,3-dimercaptosuccinic acid (DMSA;Sigma, St. Louis, Mo.) in drinking water (1.2 mg/ml and 1.5 mg/ml,respectively), starting one day before injection with ²²⁵Acnanogenerator and continued until the animals were sacrificed. Thecontrol animals received regular drinking water. Animals (n=5 per group)were sacrificed at 6 and 72 hours post-injection by carbon-dioxideasphyxiation.

[0077] Samples of blood taken by cardiac puncture, of kidneys, of liverand of small intestine were removed. The organs were washed in distilledwater, blotted dry on gauze, weighed, and the activity of ²²¹Fr (185-250keV window) and ²¹³Bi (360-480 keV window) was measured using a gammacounter (COBRA II, Packard Instrument Company, Meriden, Conn.). Samplesof the injectate (100 μl) were used as decay correction standards.Adjustment was made for the small percentage of bismuth activity thatcounted in the francium activity window. Percentage injected dose of²²⁵Ac, ²²¹Fr and ²¹³Bi per gram of tissue weight (% ID/g) was calculatedfor each animal at the time of sacrifice, using the equation (78):

A ₂₍₀₎ =[A ₂ −A _(2(eq))·(e ^(−λ2t) −e ^(−λ1t))]·e ^(λ2t)

[0078] where λ1 and λ2 are the decay constants of Ac and Bi,respectively. The mean % ID/g was determined for each experimentalgroup.

[0079] The renal ²¹³Bi activity differed significantly between the DMPSor DMSA treated groups and untreated controls at 6 hours (ANOVA,p<0.0001) and 72 hours (ANOVA, p<0.0001) post-injection with the ²²⁵Acnanogenerator (FIG. 3A). The 6 hour renal ²¹³Bi activity in the controlgroup was 95.7±3.8% ID/g, which was reduced to 38.6±5.5% ID/g and66.0±1.9% ID/g in DMPS and DMSA treated groups, respectively. A similarreduction in the renal 213Bi activity was observed at 72 hourspost-injection of 66.7±7.9% ID/g in controls versus 21.7±2.1% ID/g and41.4±7.3 in DMPS and DMSA treated groups, respectively. DMPS wassignificantly more effective than DMSA in preventing the renal ²¹³Biaccumulation at both time-points (6 h, p<0.001;72 h, p<0.001). The renal²²¹Fr activity, however, was not significantly different between theexperimental groups at either 6 hours (ANOVA, p=0.39) or 72 hours(ANOVA, p=0.20) post-injection (FIG. 3A).

[0080] As shown in FIG. 3B, the mean blood ²¹³Bi activity was higher (6h, ANOVA p<0.0001;72 h, ANOVA p<0.0001) in the DMPS (9.2±0.5% ID/g and5.5±0.1% ID/g at 6 and 72 hours, respectively) and DMSA (5.8±0.5% ID/gand 4.8±0.6% ID/g at 6 and 72 hours, respectively) treated groups ascompared to the controls with 1.8±0.1% ID/g and 1.5±0.7% ID/g at 6 and72 hours, respectively. However, the blood ²²¹Fr activity was unalteredby chelation therapy (data not shown). Similar results were seen withcalcium-diethylenetriamine pentaacetate (Ca-DTPA), but it was lesseffective than DMPS in reducing the renal ²¹³Bi activity (data notshown).

[0081] In plasma the dithiol chelators are transported free or asdisulfides with plasma proteins and non-protein sulfhydryl compounds,e.g. cysteine (79). In human plasma, DMPS has been shown to formnon-protein sulfhydryls to a greater extent at 37%, than DMSA at 8%.Therefore, DMPS is thought to be more reactive in plasma than DMSA (79).Also, it is believed that the presence of charged carboxyl groups impedethe transport of DMSA through cell membranes (80).

[0082] These factors may account for the greater effectiveness of DMPSin reducing the renal ²¹³Bi uptake, as compared to DMSA. DMPS, beingmore reactive, is rapidly oxidized in aqueous solutions to formdi-sulfides (81). However, a loss of efficacy was not observed when DMPSwas administered in drinking water. This possibly is due to disulfidereduction in the renal tubular cells by a glutathione-disulfide exchangereaction, to yield the parent drug. This effect has been shown inprevious studies (79).

[0083] The increase in the blood ²¹³Bi activity with chelation therapymay have resulted from the chelation and retention of ²¹³Bi generated inblood from the circulating ²²⁵Ac nanogenerators or from the extractionof tissue ²¹³Bi into the blood stream. The circulating chelator-²¹³Bicomplex is not expected to cause any significant toxicity due to theshort path length of alpha particles (50). In contrast, the reduction inthe renal ²¹³Bi activity is critical to the safety of the ²²⁵Acnanogenerators.

EXAMPLE 6

[0084] Diuretic Therapy

[0085] Mice were randomized to furosemide treatment, chlorthiazide (CTZ)treatment or no treatment(control)groups (5 animals per group).Furosemide and CTZ were administered intraperitoneally (i.p.). Theloading doses of furosemide and CTZ were 250 mg/kg and 750 mg/kgrespectively, administered one hour before ²²⁵Ac nanogeneratorinjection.The maintenance doses were 100 mg/kg and 300 mg/kg, respectively,administered 12 hours and 24 hours after the loading dose. The controlswere injected with an equal volume of saline (vehicle).

[0086] Alternatively, mice received DMPS (1.2 mg/ml in drinking water)and either furosemide or CTZ i.p using the same dose schedule as above.The controls received regular drinking water and were injected with anequal volume of saline. The animals were sacrificed at 24 hourspost-injection with the labeled antibody and the mean activity (% ID/g)of ²²⁵Ac, ²²¹Fr and ²¹³Bi in blood and kidneys was calculated for eachexperimental group, as described above.

[0087] Diuretic therapy prevented the renal accumulation of both ²²¹Frand ²¹³Bi (FIG. 4A). The 24 hour renal ²²¹Fr activity differedsignificantly (ANOVA, p<0.0001) between the experimental groups(21.9±1.0% ID/g in controls versus 11.8±0.4% ID/g and 9.7±0.4% ID/g infurosemide and CTZ treated groups, respectively). Similarly, the 24 hourrenal ²¹³Bi activity was 38.7±1.0% ID/g in the controls versus 18.3±0.6%ID/g and 18.6±1.6% ID/g in furosemide and CTZ treated groups,respectively(ANOVA, p<0.0001). However, the renal ²²¹Fr and ²¹³Biactivities were not significantly different between the two treatedgroups (Bonferroni's post-hoc analysis, p>0.05 for both ²²¹Fr and ²¹³Biactivities).

[0088] Furthermore, the combination of DMPS with a diuretic, furosemideor CTZ, caused a greater reduction of ˜75-80% in the renal ²¹³Biactivity than seen with DMPS or diuretics alone (FIGS. 4A-4B). The 24hour renal ²¹³Bi activity was 45.7±1.0% ID/g in controls versus10.4±1.0% ID/g and 10.5±1.5% ID/g in DMPS+furosemide and DMPS+CTZgroups, respectively (ANOVA, p<0.0001). The reduction in the renal ²²¹Fraccumulation, however, was similar to that seen with diuretic treatment(25.7±1.3% ID/g in controls versus 9.7±0.4% ID/g and 13.3±1.4% ID/g inDMPS+furosemide and DMPS+CTZ groups, respectively (ANOVA, p<0.0001).

[0089] Different classes of diuretics inhibit the tubular reabsorptionof the alkali metals, Na⁺ or K⁺ or both, although they differ in theirpotency, mechanism and site of action within the nephron. Furosemide andCTZ act, respectively, in the ascending limb of Henle's loop and distalconvoluted tubule of the nephron (82). The significant drop in the renal²²¹Fr activity with furosemide and CTZ possibly is due to an inhibitionof the renal tubular reabsorption of ²²¹Fr which is an alkali metal andis, therefore, expected to behave like Na⁺ and K⁺. Since ²¹³Bi isgenerated from ²²¹Fr, a decrease in the renal ²¹³Bi ensued. Furthermore,the combination of DMPS with a diuretic, e.g., furosemide or CTZ,resulted in an even greater reduction in renal ²¹³Bi activity than seenwith DMPS or the diuretics alone. The administered doses of furosemideand CTZ were scaled from previously published literature on their ED₅₀in mice. The doses exceed the human therapeutic doses as there is aspecies difference in the ED₅₀ of these drugs (83).

EXAMPLE 7

[0090] Competitive Metal Blockade

[0091] Mice (5 per group) were injected i.p. with 200 μl of 1% bismuthsubnitrate (BSN; Sigma, St. Louis, Mo.) suspension (100 mg/kg) or anequal volume of saline (controls) 4 hours before ²²⁵Ac nanogeneratorinjection. These animals were sacrificed at 6 hours post-injection withthe ²²⁵Ac nanogenerator. Alternatively, mice were injected i.p. with 200μl of 1% BSN suspension, 4 hours before and 8 and 20 hours after ²²⁵Acnanogenerator injection (n=5) or an equal volume of saline (n=5). Theseanimals were sacrificed 24 hours after ²²⁵Ac nanogenerator injection.The mean % ID/g of ²²⁵Ac, ²²¹Fr and ²¹³Bi in blood and kidneys atsacrifice-time was calculated for each experimental group.

[0092] Competitive blockade of ²¹³Bi binding-sites in the renal tubularcells by non-radioactive bismuth resulted in a moderate, butsignificant, reduction in the renal ²¹³Bi activity at both 6 hour(p=0.004) and 24 hour (p<0.0001) time-points (FIG. 5). Renal ²¹³Biactivity at 6 and 24 hours post-injection was 57.5±2.4% ID/g and64.9±1.2% ID/g, respectively in controls versus 46.1±1.4% ID/g and48.2±0.6% ID/g, respectively in BSN treated animals. As expected, therenal ²²¹Fr activity was unaltered (FIG. 5) at either time-point (6hours, p=0.10;24 hours, p=0.61).

EXAMPLE 8

[0093] Effect of DMPS on Tumor Burden

[0094] Disseminated human Daudi lymphoma (84) treated with ²²⁵Ac labeledanti-CD19, was used as the model system. SCID mice, 10-12 weeks old,were randomized to “low tumor burden” or 7 days growth of tumor, “hightumor burden” or 30 days growth of tumor or “high tumor burden+DMPS”group or 30 days growth of tumor and treated with 1.2 mg/ml DMPS indrinking water, starting one day before injection with ²²⁵Acnanogenerator. All mice were injected intravenously with 5×10⁶ Daudilymphoma cells in 0.1 ml phosphate buffered saline (PBS). The “lowburden” animals were injected with the tumor cells 23 days after the“high burden” ones. The animals were checked daily for the onset ofhind-leg paralysis. 30 days after injection of tumor cells in the “highburden” animals and 7 days after injection for the “low burden” group,all animals were injected retro-orbitally with 0.5 μCi of ²²⁵Ac labeledSJ25C1 in 100 μl.

[0095] The animals (5 per group) were sacrificed at 24 hourspost-injection and the mean ²²⁵Ac, ²²¹Fr and ²¹³Bi activity (% ID/g) inblood, femurs and kidneys was calculated for each experimental group.The % of human-CD20 positive cells in the femoral bone marrow wasestimated in one representative animal from the “high and low burden”groups by flow cytometric staining with phycoerythrin (PE)-conjugatedanti-human CD20 (BD, San Jose, Calif.) and compared to that of a nontumor-bearing mouse of the same strain.

[0096] The expression of CD19 and CD20 antigens and binding of theantibody (SJ25C1) to CD19 on Daudi cells were confirmed by flowcytometry before injecting the tumor in animals. The percentage oftarget lymphoma cells, i.e., bone marrow cells positive for human CD20,in one representative “low burden” and “high burden” animal were 0.12%and 27.5%, respectively (FIG. 6A). Due to higher localization of thelabeled antibody (²²⁵Ac activity) to the femurs, the kidneys to femuractivity ratios for ²²⁵Ac were significantly lower (p<0.0001) in thegroups with higher tumor burden (FIG. 6B).

[0097] As demonstrated in FIG. 6C, the presence of a higher tumor burdenresulted in a significant decrease in the renal ²¹³Bi activity,(52.6±3.1% ID/g, in “low burden” versus 38.8±1.3% ID/g in “high burden”animals; p=0.003), which was reduced further by DMPS treatment(16.7±2.7% ID/g; p<0.0001 compared to untreated “high burden” group andp<0.0001 compared to “low burden” group). The femur ²¹³Bi activity wassignificantly higher (p<0.0001) in the untreated “high burden” group(8.5±0.5% ID/g) as compared to the “low burden” group (2.7±0.3% ID/g).However, DMPS treated “high burden” animals had lower ²¹³Bi activity(p=0.002) in the femurs (4.8±0.6% ID/g) than untreated “high burden”animals (FIG. 6C). The ratio of kidney to femur activity for ²¹³Bi wassignificantly lower (p<0.0001) in the high tumor burden group (FIG. 6B).

[0098] The presence of high levels of a specific target, i.e., tumorburden, caused a decrease in the amount of circulating, untargetedantibody and, therefore, the systemically released daughters. Thistranslated to an increase in the activity of ²²⁵Ac and its radioactivedaughters in the femurs where the tumor resided and a correspondingdecrease in their activities in the kidneys. The effect may have beenblunted by the large dose of antibody used and the low specific activityof the radioimmunoconjugate as, approximately, 1 out of 1000 antibodieswere labeled with ²²⁵Ac.

[0099] Based on the number of available CD19 sites per Daudi cell, 120million tumor cells, which is an estimated tumor load in a “high burdenanimal”, are expected to maximally absorb approximately 1.2 μg of theantibody, whereas 6.7 μg of the antibody was injected per animal. Thistranslates to an excess of injected antibodies as compared to theavailable binding sites. A typical acute myeloid leukemia patient hasapproximately 10¹²leukemia cells and based on the available CD33 sites,approximately 5 mg of HuM195 could be absorbed. However, administeringsub-saturating amounts, i.e., about 2-3 mg of antibody per patient wouldyield a more pronounced reduction in the renal daughter accumulation isexpected.

[0100] DMPS treatment further reduced the renal ²¹³Bi accumulation inanimals that bore the target tumor. Additionally, a reduction in thefemur ²¹³Bi activity was seen in these animals. However, despite thereduction in the ²¹³Bi activity in the femurs, the kidney to femuractivity ratio in these animals for ²¹³Bi was, in fact, significantlylower. This is because of a greater relative reduction in the ²¹³Biaccumulation in kidneys than in the femurs. Free bismuth has been shownto accumulate in the femurs even in the absence of a bone marrow tumor(64). Therefore, the ²¹³Bi activity in the femurs cannot be entirelyaccounted for by the ²¹³Bi inside the tumor cells. The reduction in thefemur ²¹³Bi activity may be due to its scavenging from the tumor cellsor the femurs. It also could be due to scavenging of free ²¹³Bi producedon the surface of the tumor cells as a result of the attachment of thelabeled antibody.

EXAMPLE 9

[0101] In vivo Biodistribution of [Ac]Hum195 at 24 Hours

[0102] Two cynomolgus monkeys weighing about 7 kg were injected with 25μCi of Ac-225 nanogenerators on HuM195 antibodies. One monkey receivedwater and the other received DMPS in water for 24 hours and one dose ofDMPS intravenously 90 min before sacrifice. At 24 hours the two monkeyswere sacrificed and the kidneys examined for Bi-213 daughters. A 70%reduction in Bi-213 in the kidneys of the treated monkey was found (FIG.7).

[0103] The following references are cited herein:

[0104] 1. Scheinberg D A, Maslak P M, Weiss M. Acute Leukemia. In:Cancer: Principles and Practice of Oncology; pp 2404-2432; DeVita V., etal. Eds.; Lipincott-Raven, Publishers, New York (2001).

[0105] 2. Scheinberg et al., Cancer Res. 42:44-49 (1982).

[0106] 3. Scheinberg et al., Cancer Res. 43:265-272 (1983).

[0107] 4. Scheinberg et al., J Clin Oncol 9:478-490 (1991).

[0108] 5. Nadler et al., Cancer Res 40:3147-54 (1980).

[0109] 6. Shawler et al., Cancer Res 44:5921-5927 (1984).

[0110] 7. Ritz et al., Blood 58:141-152 (1981).

[0111] 8. Scheinberg et al., Science 215:1511-1513 (1982).

[0112] 9. Gansow et al., Generator produced Bi-212 chelated tochemically modified monoclonal antibodies for use in radiotherapy. In:Radionuclide Generators: New Systems for Nuclear Medicine Application. FF Knapp, T A Butler, Eds. ACS. Washington, D.C. (1984).

[0113] 10. Kassis et al., Radiat Res 84:407-425 (1980).

[0114] 11. Sastry K S R, Rao D V. Dosimetry of low energy electrons. RaoD V, Chandra R, Graham M C. eds. In: Physics of Nuclear Medicine,American Association of Physicists in Medicine (1984).

[0115] 12. Houghton et al., Sem Oncol 13:165-179 (1986).

[0116] 13. Miller et al., Lancet 2:226-230 (1981).

[0117] 14. Foon et al., Blood 64:1085-1093 (1984).

[0118] 15. Dillman et al., J Clin Oncol 2:881-891 (1984).

[0119] 16. Scheinberg et al., J Clin Oncol 8:792-803 (1990).

[0120] 17. Denardo et al., J Clin Oncol 16:3246-3256 (1998).

[0121] 18. Hale et al., Lancet 2:1394-1399 (1988).

[0122] 19. Schwartz et al., J Clinical Oncol 11:294-303 (1993).

[0123] 20. Matthews et al., Blood 85:1122-1131 (1995).

[0124] 21. Jurcic et al., Leukemia 9:244-248 (1995).

[0125] 22. Czuczman et al., J Clin Oncol 11:2021-2029 (1993).

[0126] 23: Kaminski et al., J Clin Oncl 14:1974-1981 (1996).

[0127] 24. McLaughlin et al., J Clin Oncol 92:2825-2833 (1998).

[0128] 25. Czuczman et al., J Clin Oncol 17:268-276 (1999).

[0129] 26. Knox et al., Clin Cancer Res 2:457-470 (1996).

[0130] 27. Keating et al., Blood 94 (suppl):705 (1999).

[0131] 28. Sievers et al., Blood 93:3678-2684 (1999).

[0132] 29. Caron et al., Blood 83:1760-1768 (1994).

[0133] 30. Jurcic et al., Blood 98(9):2651-2656 (2001).

[0134] 31. Feldman et al., Proceedings of ASCO (2002).

[0135] 32. Bernstein et al., J Clin Invest 79:1153 (1987).

[0136] 33. Tanimoto et al., Leukemia 3:339-348 (1989).

[0137] 34. Scheinberg et al., Leukemia 3:440-445 (1989).

[0138] 35. Griffin et al., Leuk Res 8:521-534 (1984).

[0139] 36. Applebaum et al.,. Transplantation 54:829-833 (1992).

[0140] 37. Bloomer et al., Science 212:340-341 (1981).

[0141] 38. Garg et al., Cancer Res 50:3514-3520 (1990).

[0142] 39. Howell et al., Radiation Protection Dosimetry 31:325-328.

[0143] 40. Mackliss et al., Radiation Research 130:220-226 (1992).

[0144] 41. Humm et al.,. Radiation Research 134:143-150 (1993).

[0145] 42. Geerlings et al., Nuclear Medicine Comm. 14:121-125 (1993).

[0146] 43. McDevitt et al., Eur. J. Nuc. Med., 25 (9), 1341-1351 (1998).

[0147] 44. Vaidyanathan G, Zalutsky M R. Targeted therapy using alphaemitters. Phys Med Biol 1:1905-1914 (1994).

[0148] 45. Behr, et al., Cancer Res. 59, 2635-43 (1999).

[0149] 46. Wilber D A. Antibody, Immunoconjugates andRadiopharmaceuticals 4:85-97 (1991).

[0150] 47. Kaspersen et al., Nuclear Medicine Communications 16:468-476(1995).

[0151] 48. Brechbiel et al., J. Chem. Soc. Perkin Trans. 1, 1173-1178(1992).

[0152] 49. McDevitt et al., Cancer Res. 60:6095-6102 (2000b).

[0153] 50. Jurcic et al., Blood 100(4):1233-9 (2002).

[0154] 51. Sgouros, et al., J. of Nucl. Med. 40 (11), 1935-1946 (1999).

[0155] 52. McDevitt et al., Cell Death Differ 9(6):593-4 (2002).

[0156] 53. Chang et al., Mol Cancer Ther 1(7):553-63 (2002).

[0157] 54. Kozak et al., Proc Natl Acad Sci U S A 83(2):474-8 (1986).

[0158] 55. Bethge et al., Blood 101(12):5068-75 (2003).

[0159] 56. Yao et al., J Nucl Med 42(10):1538-44 (2001).

[0160] 57. Waldmann T A. Immunotherapy: past, present and future. NatMed 9(3):269-77 (2003).

[0161] 58. Mulford et al., Expert Opin Biol Ther 4(1):95-105 (2004).

[0162] 59. Zalutsky et al., Curr Pharm Des 6(14):1433-55 (2000).

[0163] 60. Raju et al., Radiat Res 128(2):204-9 (1991).

[0164] 61. McDevitt et al., Science 294(5546):1537-40 (2001).

[0165] 62. Borchardt et al., Cancer Res 63(16):5084-90 (2003).

[0166] 63. Meiderer et al., J Nucl Med 2004

[0167] 64. Jones et al., Nucl Med Biol 23(2):105-13 (1996).

[0168] 65. Sgouros et al., J Nucl Med 34(3):422-30 (1993).

[0169] 66. Szymanska et al., Biochem Pharmacol 26(3):257-8 (1997).

[0170] 67. Russ et al., Radiat Res 63(3):443-54 (1975).

[0171] 68. Slikkerveer et al., Med Toxicol Adverse Drug Exp 4(5):303-23(1989).

[0172] 69. Slikkerveer et al., J Lab Clin Med 119(5):529-37 (1992).

[0173] 70. Yung et al., Pharmacol Biochem Behav 21 Suppl 1:71-5 (1984).

[0174] 71. Basinger et al., J Toxicol Clin Toxicol 20(2):159-65 (1983).

[0175] 72. Slikkerveer et al., Analyst 123(1):91-2 (1998).

[0176] 73. Bruenger et al., Int J Radiat Biol 60(5):803-818 (1991).

[0177] 74. Breitenstein et al., The U.S. Experience 1958-1987,″ in: TheMedical Basis of Radiation Accident Preparedness. 2 ed: Elsevier SciencePublishing Co., Inc., 397-406 (1990).

[0178] 75. Reyes et al., Cardiovasc Drugs Ther 13(5):371-98 (1999).

[0179] 76. McDevitt et al., Appl Radiat Isot 57(6):841-7 (2002).

[0180] 77. Nikula et al., J Nucl Med 40(1):166-76 (1999).

[0181] 78. Mirzadeh et al., Radiochimica Acta 60:1-10 (1993).

[0182] 79. Maiorino et al., J Pharmacol Exp Ther 277(1):375-84 (1996).

[0183] 80. Aposhian et al., Annu Rev Pharmacol Toxicol 30:279-306(1990).

[0184] 81. Aposhian et al., Life Sci 31(19):2149-56 (1982).

[0185] 82. Puschett J B. Cardiology 84 Suppl 2:4-13 (1994).

[0186] 83. Hesdorffer et al., Ann Neurol 2001;50(4):458-62 (2001).

[0187] 84. Ghetie et al., Blood 83(5):1329-36 (1994).

[0188] Any patents or publications mentioned in this specification areindicative of the levels of those skilled in the art to which theinvention pertains. Further, these patents and publications areincorporated by reference herein to the same extent as if eachindividual publication was specifically and individually incorporated byreference.

[0189] One skilled in the art will appreciate readily that the presentinvention is well adapted to carry out the objects and obtain the endsand advantages mentioned, as well as those objects, ends and advantagesinherent herein. The present examples, along with the methods,procedures, treatments, molecules, and specific compounds describedherein are presently representative of preferred embodiments, areexemplary, and are not intended as limitations on the scope of theinvention. Changes therein and other uses will occur to those skilled inthe art which are encompassed within the spirit of the invention asdefined by the scope of the claims.

What is claimed is:
 1. A method of reducing nephrotoxicity in an individual during radioimmunotherapeutic treatment of a pathophysiological condition, comprising: administering a pharmacologically effective dose of at least one adjuvant effective for preventing accumulation of a metal in kidneys; administering an actinium-225 radioimmunoconjugate to treat the pathophysiological condition; and preventing accumulation of alpha particle-emitting daughters of said actinium-225 within the kidneys of the individual via interaction between said adjuvant and said ²²⁵Ac daughters or the kidney tissue or a combination thereof thereby reducing nephrotoxicity during the radioimmunotherapeutic treatment.
 2. The method of claim 1, wherein said adjuvant(s) is administered prior to administering said actinium-225 radioimmunoconjugate, said adjuvant(s) continuing to be administered after said actinium-225 radioimmunoconjugate.
 3. The method of claim 1, wherein said adjuvant is a chelator, a diuretic, a competitive metal blocker, or a combination thereof.
 4. The method of claim 3, wherein said chelator is 2,3 dimercapto-1-propane sulfonic acid, meso 2,3-dimercapto succinic acid, diethylenetriamine pentaacetic acid, calcium diethylenetriamine pentaacetic acid, or zinc diethylenetriamine pentaacetic acid.
 5. The method of claim 3, wherein said diuretic is furosemide, chlorthiazide, hydrochlorothiazide, bumex or other loop diuretic.
 6. The method of claim 3, wherein said competitive metal blocker is bismuth subnitrate or bismuth subcitrate.
 7. The method of claim 1, wherein said ²²⁵Ac daughter is bismuth-213, francium-221 or a combination thereof.
 8. The method of claim 1, wherein said actinium-225 radioimmunoconjugate comprises an actinium-225 bifunctional chelant and a monoclonal antibody.
 9. The method of claim 8, wherein said actinium-225 radioimmunoconjugate is [²²⁵Ac] DOTA-HuM195.
 10. The method of claim 1, wherein said pathophysiological condition is a cancer or an autoimmune disorder.
 11. The method of claim 1, wherein said cancer is a solid cancer, a disseminated cancer or a micrometastatic cancer.
 12. The method of claim 11, wherein said cancer is myeloid leukemia.
 13. A method of reducing nephrotoxicity in an individual during radioimmunotherapeutic treatment a pathophysiological condition, comprising: administering a pharmacologically effective dose of a chelator; administering an actinium-225 radioimmunoconjugate to treat the cancer; and preventing accumulation of bismuth-213 daughters of said actinium-225 within the kidneys of the individual by scavenging thereof with said chelator thereby reducing nephrotoxicity during the radioimmunotherapeutic treatment.
 14. The method of claim 13, wherein said chelator is administered prior to administering said ²²⁵Ac radioimmunoconjugate, said chelator continuing to be administered after said ²²⁵Ac radioimmunoconjugate.
 15. The method of claim 13, wherein said chelator is 2,3 dimercapto-1-propane sulfonic acid, meso 2,3-dimercapto succinic acid, diethylenetriamine pentaacetic acid, calcium diethylenetriamine pentaacetic acid, or zinc diethylenetriamine pentaacetic acid.
 16. The method of claim 13, further comprising: administering a pharmacologically effective dose of a diuretic; and preventing accumulation of francium-211 daughters of said actinium-225 within the kidneys of the individual by inhibiting reabsorption of francium-211 therein with said diuretic thereby reducing nephrotoxicity during the radioimmunotherapeutic treatment.
 17. The method of claim 16, wherein said diuretic is administered prior to administering said ²²⁵Ac radioimmunoconjugate, said diuretic continuing to be administered after said ²²⁵Ac radioimmunoconjugate.
 18. The method of claim 16, wherein said diuretic is furosemide, chlorthiazide, hydrochlorothiazide, bumex, or other loop diuretic.
 19. The method of claim 13, wherein said ²²⁵Ac radioimmunoconjugate comprises an actinium-225 bifunctional chelant and a monoclonal antibody.
 20. The method of claim 19, wherein said ²²⁵Ac radioimmunoconjugate is [²²⁵Ac] DOTA-HuM195.
 21. The method of claim 13, wherein said pathophysiological condition is a cancer or an autoimmune disorder.
 22. The method of claim 21, wherein said cancer is a solid cancer, a disseminated cancer or a micrometastatic cancer.
 23. The method of claim 22, wherein said cancer is myeloid leukemia.
 24. A method of reducing nephrotoxicity in an individual during radioimmunotherapeutic treatment of a pathophysiological condition, comprising: administering a pharmacologically effective dose of a diuretic; administering an actinium-225 radioimmunoconjugate to treat the cancer; and preventing accumulation of francium-211 daughters of said actinium-225 within the kidneys of the individual by inhibiting reabsorption of francium-211 therein with said diuretic thereby reducing nephrotoxicity during the radioimmunotherapeutic treatment.
 25. The method of claim 24, wherein said diuretic is administered prior to administering said ²²⁵Ac radioimmunoconjugate, said diuretic continuing to be administered after said ²²⁵Ac radioimmunoconjugate.
 26. The method of claim 24, wherein said diuretic is furosemide, chlorthiazide, hydrochlorothiazide, bumex, or other loop diuretic.
 27. The method of claim 24, wherein said ²²⁵Ac radioimmunoconjugate comprises an actinium-225 bifunctional chelant and a monoclonal antibody.
 28. The method of claim 27, wherein said ²²⁵Ac radioimmunoconjugate is [²²⁵Ac] DOTA-HuM195.
 29. The method of claim 24, wherein said pathophysiological condition is a cancer or an autoimmune disorder.
 30. The method of claim 29, wherein said cancer is a solid cancer, a disseminated cancer or a micrometastatic cancer.
 31. The method of claim 30, wherein said cancer is myeloid leukemia.
 32. A method of improving radioimmunotherapeutic treatment of cancer in an individual, comprising: administering a pharmacologically effective dose of a chelator; administering an actinium-225 radioimmunoconjugate; and scavenging bismuth-213 daughters of the actinium-225 with said chelator to reduce nephrotoxicity in the individual during the treatment thereby increasing the therapeutic index of the actinium-225 to improve the treatment for said cancer.
 33. The method of claim 32, wherein said chelator is administered prior to administering said ²²⁵Ac radioimmunoconjugate, said chelator continuing to be administered after said ²²⁵Ac radioimmunoconjugate.
 34. The method of claim 32, wherein said chelator is 2,3 dimercapto-1-propane sulfonic acid, meso 2,3-dimercapto succinic acid, diethylenetriamine pentaacetic acid, calcium diethylenetriamine pentaacetic acid, or zinc diethylenetriamine pentaacetic acid.
 35. The method of claim 32, further comprising: administering a pharmacologically effective dose of a diuretic; and inhibiting renal uptake of francium-211 daughters of the actinium-225 with said diuretic to reduce nephrotoxicity in the individual during the treatment thereby increasing the therapeutic index of the actinium-225 to improve the treatment for-said cancer.
 36. The method of claim 35, wherein said diuretic is administered prior to administering said ²²⁵Ac radioimmunoconjugate, said diuretic continuing to be administered after said ²²⁵Ac radioimmunoconjugate.
 37. The method of claim 35, wherein said diuretic is furosemide, chlorthiazide, hydrochlorothiazide, bumex, or other loop diuretic.
 38. The method of claim 35, wherein said ²²⁵Ac radioimmunoconjugate comprises an actinium-225 bifunctional chelant and a monoclonal antibody.
 39. The method of claim 38, wherein said ²²⁵Ac radioimmunoconjugate is [²²⁵Ac] DOTA-HuM195.
 40. The method of claim 35, wherein said cancer is a solid cancer, a disseminated cancer or a micrometastatic cancer.
 41. The method of claim 40, wherein said cancer is myeloid leukemia.
 42. A method of improving radioimmunotherapeutic treatment of cancer in an individual, comprising: administering a pharmacologically effective dose of a diuretic; administering an actinium-225 radioimmunoconjugate; and inhibiting renal uptake of francium-211 daughters of the actinium-225 with said diuretic to reduce nephrotoxicity in the individual during the treatment thereby increasing the therapeutic index of the actinium-225 to improve the treatment for said cancer.
 43. The method of claim 42, wherein said diuretic is administered prior to administering said ²²⁵Ac radioimmunoconjugate, said diuretic continuing to be administered after said ²²⁵Ac radioimmunoconjugate.
 44. The method of claim 42, wherein said diuretic is furosemide, chlorthiazide, hydrochlorothiazide, bumex, or other loop diuretic.
 45. The method of claim 42, wherein said ²²⁵Ac radioimmunoconjugate comprises an actinium-225 bifunctional chelant and a monoclonal antibody.
 46. The method of claim 45, wherein said ²²⁵Ac radioimmunoconjugate is [²²⁵Ac] DOTA-HuM195.
 47. The method of claim 42, wherein said cancer is a solid cancer, a disseminated cancer or a micrometastatic cancer.
 48. The method of claim 47, wherein said cancer is myeloid leukemia.
 49. A method of increasing the therapeutic index of an actinium-225 radioimmunoconjugate during treatment of a pathophysiological condition in an individual comprising: inhibiting renal uptake of at least one alpha particle-emitting daughter of actinium-225 whereby nephrotoxicity is reduced during the treatment thereby increasing the therapeutic index of said actinium-225 radioimmunoconjugate.
 50. The method of claim 49, wherein inhibiting renal uptake of said ²²⁵Ac daughter(s) comprises: administering a pharmacologically effective amount of an adjuvant comprising: a chelator to scavenge said ²²⁵Ac daughters therewith; or a diuretic to inhibit reabsorption of said ²²⁵Ac daughters within a kidney; or a competitive metal blocker to prevent binding of said ²²⁵Ac daughters within a kidney; or a combination thereof.
 51. The method of claim 50, wherein said chelator and/or said diuretic and/or said competitive metal blocker are administered prior to treatment with said actinium-225 radioimmunoconjugate, said chelator and/or said diuretic continuing to be administered after said actinium-225 radioimmunoconjugate is administered to the individual.
 52. The method of claim 50, wherein said chelator is 2,3 dimercapto-1-propane sulfonic acid, meso 2,3-dimercapto succinic acid, diethylenetriamine pentaacetic acid, calcium diethylenetriamine pentaacetic acid, or zinc diethylenetriamine pentaacetic acid.
 53. The method of claim 50, wherein said diuretic is furosemide, chlorthiazide, hydrochlorothiazide, bumex, or other loop diuretic.
 54. The method of claim 50, wherein said competitive metal blocker is bismuth subnitrate or bismuth subcitrate.
 55. The method of claim 50, wherein said chelator scavenges the ²²⁵Ac daughter bismuth-213.
 56. The method of claim 50, wherein said diuretic inhibits reabsorption of the ²²⁵Ac daughter francium-211.
 57. The method of claim 50, wherein said competitive metal binder prevents binding of the ²²⁵Ac daughter bismuth-213.
 58. The method of claim 49, wherein said actinium-225 radioimmunoconjugate is [²²⁵Ac] DOTA-HuM195.
 59. The method of claim 49, wherein said pathophysiological condition is a cancer or an autoimmune disorder.
 60. The method of claim 59, wherein said cancer is a solid cancer, a disseminated cancer or a micrometastatic cancer.
 61. The method of claim 60, wherein said cancer is myeloid leukemia. 